“Now he will be slapping paints on paper with other sex criminals. But if he wants to be released early then he must complete the course. In a fashion that shows he has accepted that he has caused deep pain to his victims.”

The offender course at Bullingdon jail in Oxfordshire lasts for several weeks with six-hour sessions.

The Prison Service said: “Prisoners in behaviour programmes receive a minimal amount if they participate in purposeful activity.”